Highly recommended. Over the past few years, there has
been a
flowering of academic research into the nature of networks
such as the
link structure of the World Wide Web and social networks.
This book
collects some of the highlights of this research, and
presents them as
well-written stories. Barabási makes a strong case
that network
thinking will have profound implications over the coming
years, not
just for the World Wide Web, but for biology, social
networks, and
other areas of science as well.

"Scale-free" networks have a central place in the book, not
surprising
as Barabási is co-author of a groundbreaking paper on
the subject.
The original paper dealt with the Web, but subsequent
research has
turned up a number of other networks with similar topology. Even
within the Internet, scale-free topology applies both to the
network
of routers and backbones as well as the link structure of
the Web.

Scale-free networks are instantly recognized by their
characteristic
power-law degree distribution. There are a few
highly-connected nodes,
and many nodes with just one or two links. By contrast, the
degree
distribution in random networks tends to be a tightly
clustered bell
curve.

A simple model generates randomized scale-free networks.
Start with a
small seed network, possibly a single node. For each new
node, add a
link from that node to existing nodes, with probability
proportional
to the indegree of the existing node. Thus, the model
captures both
growth and preferential attachment. If either element is
missing, the
resulting network is not scale-free.

These networks have a few important properties. First, their
diameter
is very small. This property has been known in social
network theory
since the brilliant "small world" experiments of Milgram in
1967. The
idea was popularized in the 1990 play by John Guare, "Six
Degrees of
Separation", and has since entered the popular vocabulary.

Second, such a network stays well connected even when random
nodes are
removed. This is an "attack resistance" property of the
network, not
directly related to the attack resistance of trust metrics,
my own
specialty (although the underly concept of network flow plays an
important role in the analysis of both).

However, when a few highly connected nodes are removed, the
network
fragments. Thus, scale-free networks are in this way more
vulnerable than random networks.

Barabási does not address trust metrics. This is a
bit surprising,
because Google plays a part in the book, as a "more fit"
search engine
that rapidly becomes a hub even though existing search
engines such as
Inktomi and Altavista have already established names for
themselves.
Barabási misses the opportunity to explain why
Google is
better. Also, Gaure's play deals with a con artist who is
expert at
playing his social network to further his own goals, but
Barabási does
not pursue the theme of trust (and violation of that trust)
in social
networks.

Even if you are familiar with scale-free network theory, the
book is
still a fun read, and the presentation may be helpful in
talking with
others. For people involved in Internet software design, and
in design
of p2p networks, this book is essential reading. The book nicely
balances an accessible presentation with meaty intellectual
content.
Most people who enjoy thinking about the world will find
something of
interest.